The p38 MAPK inhibitor, PD169316, inhibits transforming growth factor beta-induced Smad signaling in human ovarian cancer cells

Transforming growth factor beta (TGFbeta) can signal through a variety of Smad-independent pathways, including the p38 MAPK pathway. Recent work has shown that inhibitors of p38 MAPK, such as SB203580 and SB202190, can inhibit signaling induced by TGFbeta. Here we show that another p38 MAPK inhibitor, PD169316, abrogates signaling initiated by both TGFbeta and Activin A, but not bone morphogenetic protein (BMP) 4. Inhibition of TGFbeta signaling is dose dependent and results in reduced Smad2 and Smad3 phosphorylation, nuclear translocation, and up-regulation of the TGFbeta target gene Smad7. Reduced TGFbeta signaling is not due to abrogation of p38 MAPK activity, since blocking p38 MAPK activity with a dominant negative form of p38 MAPK has no effect on TGFbeta/Smad signaling. Our results show that use of PD169316 at 5 MICROM or higher can block TGFbeta signaling activity and thus caution must be used when attributing cellular activities exclusively to p38 MAPK signaling when these inhibitors are used experimentally.     

Ethical Research Issues: Going Beyond the Declaration of Helsinki

La Vaque and Rossiter made a strong, supported argument that it is unethical to use a no treatment control group in a research study if a known, effective treatment is available. Their argument is based on the supposition that the Declaration of Helsinki is the ethical world standard for research with humans. Their argument appears to be straightforward, but is not simple to apply. The issues are very complex, include issues not discussed in their argument, and can lead to a different conclusion as pointed out in this paper. The World Medical Association developed the Declaration of Helsinki as one of their official policies. The Declaration of Helsinki, however, is not accepted as the world ethical standard, as demonstrated by its lack of adoption by many professional associations or even by the United States Federal Government. Perhaps it is not mentioned because its ethical provisions are aspirational rather than mandatory as implied by La Vaque and Rossiter. Researchers and clinicians should also be aware of other ethical issues not directly discussed in the La Vaque and Rossiter paper. The Belmont Report is the basis for the ethical protection of human research subjects for at least 17 federal agencies and does not mention the Declaration of Helsinki. The Belmont Report mentions several ethical principles that form the basis for informed consent, risk/benefit assessment, confidentiality of data, subject selection, Institutional Review Boards, and other protections needed when doing research with human subjects. At least 2 of these core principles have direct implications to the discussion related to the use of placebo controls. The ethical principle of fidelity is also important in guiding research activities with human subjects. Researchers should be familiar with the La Vaque and Rossiter argument, the Belmont Report, and the federal policies developed to implement the provisions of that report, for example, Regulation 45 CFR 46.     

Rethinking historical controls

Inference from traditional historical controls, i.e. comparing a new treatment in a current series of patients with an old treatment in a previous series of patients, may be subject to a strong selection bias. To avoid this bias, Baker and Lindeman (1994) proposed the paired availability design. By applying this methodology to estimate the effect of epidural analgesia on the probability of Cesarean section, we made two important contributions with the current study. First, we generalized the methodology to include different types of availability and multiple time periods. Second, we investigated how well the paired availability design reduced selection bias by comparing results to those from a meta-analysis of randomized trials and a multivariate analysis of concurrent controls. The confidence interval from the paired availability approach differed considerably from that of the multivariate analysis of concurrent controls but was similar to that from the meta-analysis of randomized trials. Because we believe the multivariate analysis of concurrent controls omitted an important predictor and the meta-analysis of randomized trials was the gold standard for inference, we concluded that the paired availability design did, in fact, reduce selection bias.     

A missense mutant myostatin causes hyperplasia without hypertrophy in the mouse muscle

Myostatin, which is a member of the TGF-beta superfamily, is a negative regulator of skeletal muscle formation. Double-muscled Piedmontese cattle have a C313Y mutation in myostatin and show increased skeletal muscle mass which resulted from an increase of myofiber number (hyperplasia) without that of myofiber size (hypertrophy). To examine whether this mutation in myostatin gene affects muscle development in a dominant negative manner, we generated transgenic mice overexpressing the mutated gene. The transgenic mice exhibited dramatic increases in the skeletal muscle mass resulting from hyperplasia without hypertrophy. In contrast, it has been reported that a myostatin mutated at its cleavage site produces hypertrophy without hyperplasia in the muscle. Thus, these results suggest that (1) the myostatin containing the missense mutation exhibits a dominant negative activity and that (2) there are two types in the dominant negative form of myostatin, causing either hypertrophy or hyperplasia.     

Efficient multipoint mapping: making use of dominant repulsion-phase markers

The paper is devoted to the problem of multipoint gene ordering with a particular focus on "dominance" complication that acts differently in conditions of coupling-phase and repulsion-phase markers. To solve the problem we split the dataset into two complementary subsets each containing shared codominant markers and dominant markers in the coupling-phase only. Multilocus ordering in the proposed algorithm is based on pairwise recombination frequencies and using the well-known travelling salesman problem (TSP) formalization. To obtain accurate results, we developed a multiphase algorithm that includes synchronized-marker ordering of two subsets assisted by re-sampling-based map verification, combining the resulting maps into an integrated map followed by verification of the integrated map. A new synchronized Evolution-Strategy discrete optimization algorithm was developed here for the proposed multilocus ordering approach in which common codominant markers facilitate stabilization of the marker order of the two complementary maps. High performance of the employed algorithm allows systematic treatment for the problem of verification of the obtained multilocus orders, based on computing-intensive bootstrap and jackknife technologies for detection and removing unreliable marker scores. The efficiency of the proposed algorithm was demonstrated on simulated and real data.Communicated by J.W. Snape     

Posters Part 1

Schima superba and Pinus massoniana distributed over large areas in southern China both are dominant species at Dinghushan Biosphere Reserve. In the present study, the changes of chlorophyll fluorescence and xanthophyll cycle in the leaves of S. superba and P. massoniana exposed to simulated acid rain (SAR) were measured. When exposed to high light, the PSII photochemistry efficiency (F _v/F _m), efficiency of energy conversion in PSII (ΦPSII) and photochemical quenching (qP) of both S. superba and P. massoniana all decreased when acidity of SAR increased. Regarding non-photochemical quenching (qN), S. superba exposed to SAR had higher value than control plants, but there was no significant difference between the respective seedlings of P. massoniana. As for xanthophyll cycle of the two plant species, the leaves of S. superba exposed to SAR showed a higher content of carotenoids and a higher ability to convert violaxanthin to zeaxanthin than leaves of P. massoniana, which was consistent with S. superba exhibiting a stronger resistance to high light than P. massoniana. Although both species were susceptible to acid rain as shown by our results, P. massoniana was more susceptible compared to S. superba. These results provide an insight into how to protect the forest ecosystem at Dinghushan Biosphere Reserve.     

Molecular Basis of the Dominant Negative Effect of a Glycine Transporter 2 Mutation Associated with Hyperekplexia

Hyperekplexia or startle disease is a rare clinical syndrome characterized by an exaggerated startle in response to trivial tactile or acoustic stimuli. This neurological disorder can have serious consequences in neonates, provoking brain damage and/or sudden death due to apnea episodes and cardiorespiratory failure. Hyperekplexia is caused by defective inhibitory glycinergic neurotransmission. Mutations in the human SLC6A5 gene encoding the neuronal GlyT2 glycine transporter are responsible for the presynaptic form of the disease. GlyT2 mediates synaptic glycine recycling, which constitutes the main source of releasable transmitter at glycinergic synapses. Although the majority of GlyT2 mutations detected so far are recessive, a dominant negative mutant that affects GlyT2 trafficking does exist. In this study, we explore the properties and structural alterations of the S512R mutation in GlyT2. We analyze its dominant negative effect that retains wild-type GlyT2 in the endoplasmic reticulum (ER), preventing surface expression. We show that the presence of an arginine rather than serine 512 provoked transporter misfolding, enhanced association to the ER-chaperone calnexin, altered association with the coat-protein complex II component Sec24D, and thereby impeded ER exit. The S512R mutant formed oligomers with wild-type GlyT2 causing its retention in the ER. Overexpression of calnexin rescued wild-type GlyT2 from the dominant negative effect of the mutant, increasing the amount of transporter that reached the plasma membrane and dampening the interaction between the wild-type and mutant GlyT2. The ability of chemical chaperones to overcome the dominant negative effect of the disease mutation on the wild-type transporter was demonstrated in heterologous cells and primary neurons.